1. Field of the Invention
The present invention relates to a roll-rod for a vehicle, and more particularly, to a roll-rod for a vehicle in which an insulator is molded integrally with a bracket to damp large-displacement vibration and small-displacement vibration more efficiently.
2. Description of Related Art
Automobiles primarily employ monocoque bodies which are light in weight and excellent in productivity instead of frame bodies. The monocoque body is a structure in which an additional frame is removed and in the monocoque body, a power train where an engine and a transmission are coupled to each other is mounted directly on an engine room of a vehicle body. Therefore, since the vehicle body itself acts as a frame in the monocoque body, suspension and chassis parts are mounted on the monocoque body, respectively, but vibration of the power train is prevented from being transferred directly to the vehicle body and a subframe is mounted on a lower part of a vehicle in order to disperse an impact when the vehicle collides.
A suspension device and a steering device are mounted on the subframe, which is connected to a lower part of the power train through a roll-rod. That is, as shown in FIG. 1A, an engine mount and a transmission mount are mounted on both sides of the vehicle body to support a load of the power train and the roll-rod mounted on the subframe shares displacement controlling and vibration damping of the power train.
The structure of the known roll-rod is shown in FIG. 1B. Referring to FIG. 1B, the roll-rod includes a roll-rod body, a front insulator, a bracket, a rear insulator, an end plate, and a fastening bolt. The roll-rod body has a bar shape. A bush is coupled to a front portion of the roll-rod body protruding from the subframe and coupled to the power train and an inner pipe protrudes from an end surface of a rear portion of the roll-rod body inserted into the subframe. The front insulator, the bracket, the rear insulator, the end plate, and the fastening bolt are sequentially mounted on the inner pipe. The front insulator and the rear insulator are made of an elastic material and are partitioned by a partition wall formed in the bracket. In addition, the fastening bolt fastens the end plate and penetrates the inner pipe, and the end of the fastening bolt protrudes to be fixed by a nut. Therefore, the front insulator and/or rear insulator are/is elastically compressed according to movement and vibration of the roll-rod body where the bracket is fixed to the subframe.
That is, when the vehicle moves forward, the rear insulator is compressed according to the displacement of the power train by inertia to perform a damping function and when the vehicle moves backward or decelerates, the front insulator is compressed to perform the damping function.
Meanwhile, since insulators which are elastic bodies are separated from each other in a known roll-rod, a tensile load is not generated, but only a compression load acts on each of the insulators, and as a result, the known roll-rod is advantageous in durability.
However, in the case in which compression force is applied horizontally, vibration damping rate deteriorates to cause a bush to be twisted or impacted and it is difficult to control damping depending on vibration characteristics. In particular, since insulators are manufactured simply in a bucket shape without a curve, damping efficiency of small-displacement vibration deteriorates. Further, an assembly process is not simple and when the insulator is mounted in a twisted state, an assembly error occurs.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.